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Table of Contents
EDITORIAL
Year : 2022  |  Volume : 4  |  Issue : 1  |  Page : 1-2

Assessment of left ventricular systolic function


Department of Cardiology, KIMSHEALTH, Thiruvananthapuram, Kerala, India

Date of Submission19-May-2022
Date of Decision27-May-2022
Date of Acceptance27-May-2022
Date of Web Publication30-Jun-2022

Correspondence Address:
Dr. Govindan Vijayaraghavan
KIMSHEALTH, Thiruvananthapuram - 695 029, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ACCJ.ACCJ_11_22

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How to cite this article:
Vijayaraghavan G. Assessment of left ventricular systolic function. Ann Clin Cardiol 2022;4:1-2

How to cite this URL:
Vijayaraghavan G. Assessment of left ventricular systolic function. Ann Clin Cardiol [serial online] 2022 [cited 2022 Sep 29];4:1-2. Available from: http://www.onlineacc.org/text.asp?2022/4/1/1/349334



Ejection fraction (EF) is the method of expressing the systolic function of the left ventricle, and it is familiar to cardiologists and cardiac surgeons alike. While using the echo techniques, the age-old method of calculating the EF from M-mode echocardiography was found to be erratic, and this was replaced by two-dimensional (2D) echo method using the Simpson's rule, using the four-chamber and two-chamber views. However, the flaw in this technique is the foreshortening of the apical views, and this could be overcome by the 3D imaging technique when it is available. Measuring the end systolic and end diastolic volumes EF is calculated from angiocardiograms. Similar methods were used by magnetic resonance imaging, computed tomography, gated equilibrium radionuclide angiography, and gated myocardial perfusion imaging with either single-photon emission computed tomography or positron emission tomography. All these techniques utilize ventricular volumes measured at end-diastole and end-systole. Does this give you the true picture of systolic performance of the left ventricle?

Speckle-tracking echocardiography measures segmental myocardial deformation or segmental myocardial function and is different from the above methods. This technique measures the strain images of the left ventricle. When you find the hypertrophied left ventricular (LV) muscle in hypertrophic cardiomyopathy, aortic stenosis, or systemic hypertension, we always equate it with better LVEF and good LV function. When we do speckle-tracking myocardial deformation imaging, we find that this is not true. Many segments of the myocardium which is hypertrophied show reduced strain. These segments demonstrate less than normal LV function and reduced myocardial performance. It is well known that hypertrophy is pathological and has many components to it. The hypertrophied muscle does not get enough blood and has scarring and fibrosis. Moreover, there will be myofiber disarray typically seen in hypertrophic cardiomyopathy. These changes cause dispersion of myocardial electrical activity and mechanical performance. These reasons reduce the myocardia strain which will be reflected in LV global and segmental strain imaging.

Strain imaging is done using the three apical imaging planes, namely apical long-axis, apical four-chamber, and two-chamber views [Figure 1]. The results are depicted in the quad screen and in the bull's eye images. Analysis of the quad screen images from the three imaging planes will reveal the exact reduction of systolic performance of LV in each.
Figure 1: Strain curves from the three imaging planes and the composite bull's eye picture of strain in all 17 myocardial segments. Normal strain curves are depicted below the zero baseline (normal more than −16%). Peak strain is at the end of systole marked by the green vertical line. Please note that this patient has peak strain at various timings in systole and the strain curves do not reach the −16% in any of the myocardial segments Peak strain is less than normal. There is dispersion of peak strain in relation to timing and magnitude. You could also see that some myocardial segments are going above the zero baseline showing positive strain and are depicted in blue color in the bull's eye picture. Look at the 2D echo picture of left ventricular hypertrophy and an LVEF of 68%. The average global strain was only −8.2%. LVEF: Left ventricular ejection fraction

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Let us see the images from a patient with hypertrophic cardiomyopathy with LVEF of 72%. Interventricular septal thickness was 35 mm a level at which sudden cardiac death can occur in these patients. Hypertrophy was more in the mid- and apical segments. The global strain was −13.2%. Basal septal and basal lateral wall strain values were -13% and -−10%, mid-septal and mid lateral wall strain −3 % and −7%, apical septal and apical lateral strain was only −1 and −3% [Figure 2]. With increasing thickness, there were decreasing strain values or systolic function. We have to conclude that with increasing thickness, we have increasing fibrosis and myofiber disarray reducing systolic function. This is in addition to the diastolic dysfunction of the hypertrophied heart.
Figure 2: Left panel shows four-chamber view of the left ventricle. Right panel strain values and curves. Please note that the strain values of the basal mid- and apical segments in the apical long-axis view. Note the least strain is in the maximally hypertrophied apical segments

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What are we assessing by systolic function of the left ventricle? Main function of the left ventricle is the systolic ejection percentage assessed by the EF. It is achieved mainly by the contraction of the longitudinal subendocardial fibers. Longitudinal function contributes to 60% of LV ejection. However, in a hypertrophied ventricle, we are assessing the LV function by only volumetric measures. It is obvious that the real systolic function is not assessed by the EF but only by the LV strain. Strain images reveal all the weaknesses of the hypertrophied ventricle and will represent the natural history of the disease. We have to realize that the electrical and mechanical dispersion of LV muscle will make the left ventricle unstable and create nidus for sudden cardiac death.

Recent introduction of speckle-tracking echocardiography at high frame rates improved the temporal resolution of images. It is not yet a clinical tool for us to comment on.

Measurement of longitudinal strain is a new entrant in clinical cardiology and requires adequate training before the values are acceptable. Karlson et al. found that it is a more reproducible measurement of LV systolic function than EF, with adequate echocardiographic training. Using well-trained echocardiographers, they did LVEF and longitudinal strain in a group of subjects. They found that the data points were scattered widely with an r-value of 0.71 for LVEF measurement, while data points were close to the line of identity with an r-value of 0.94 for measurement of longitudinal strain. It is interesting to note that many workers found significant abnormalities in longitudinal strain in heart failure with preserved EF where the systolic function was found to be normal or near normal when measured with the conventional method of assessing systolic function with LVEF. We clinicians have to get used to the new measurement of myocardial strain, especially the longitudinal strain for assessment of systolic function of the left ventricle. So far, radial strain and circumferential strain did not show a significant correlation with LVEF. It is easier to train echocardiographers to do longitudinal strain with reasonable intra-observer and inter-observer variation. All the echo laboratories should wake up to the usefulness of longitudinal strain and should introduce longitudinal strain as a routine echo measurement.




    Figures

  [Figure 1], [Figure 2]



 

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